Transfer printing is a well-known printing process, especially in the field of printing on a non-flat article, in which a dye is transferred from a dye-sheet to a receiver sheet by stimuli (heat or/and pressure) to form a pattern and/or image on the receiver sheet. As in transfer printing, the dye sheet is intimately contacted with the receiver sheet, and the stimuli are applied to the dye sheet to cause the dye on the dye-sheet to transfer to the receiver sheet, and the dye sheet and receiver sheet are then separated.
Conventionally, the printing dye-sheet for transfer printing patterns and/or images thereon to a receiver sheet is formed by, referring to FIG. 5, a base L which comprises a transparent substrate 52, a first layer of binder 54 and a layer of transparent polyethylene terephthalate (PET) 56 being coated onto the binder 54; a dye 58 forming a pattern and/or an image which is printed onto the base L (i.e. onto the transparent polyethylene terephthalate (PET) 56), a layer of polypropylene resin 59, a second layer of binder 57, and a layer of releasing paper 60. According to the conventional printing-sheet, the dye 58 is enclosed between the layer of transparent polyethylene terephthalate (PET) 56 and the layer of polypropylene resin 59. The object of the layer of polypropylene resin 59 is to enhance the brightness of the dye 58.
The conventional transfer printing dye sheet is produced by the process of, referring to FIG. 4, 1) printing a dye 58 onto the base L, wherein the dye 58 is formed by 50 wt % of solid dye with 50 wt % of solvent, and the a solvent is xylene or cyclohexanone as is used in the conventional process. 2) cutting the layer of polyethylene terephthalate (PET) 56 and binder 54 along the outer boundary of the pattern and/or image on the polyethylene terephthalate (PET) 56 with a cutting instrument; 3) separating the portion of polyethylene terephthalate (PET) 56 and binder 54 which have been cut off; 4) brightening the dye 58 by covering it with a layer of polypropylene resin 59; 5) finishing: coating a second layer of binder 57 on the polypropylene resin 59, and covering a layer of releasing paper 60 onto the second layer of binder 57.
The time required to dry the dye 58 of step 1) is usually about 20-25 minutes, and the other steps require considerably longer time, thus, the conventional process is not suitable for mass production. In order to fit the profile of the pattern and/or image on the polyethylene terephthalate (PET) 56, the cutting instrument used in step 2) must be specifically designed and produced because of the irregularity of the pattern and/or image, thus, extra cost will be incurred. Additionally, also for the reason of the irregularity of the pattern and/or image, it is impossible to automatically separate the portion of polyethylene terephthalate (PET) 56 and binder 54 which have been cut off by the cutting instrument, that is, the step of separating must be completed manually.
As per the conventional printing dye-sheet 50 being used, the releasing paper 60 is firstly separated, then the dye-sheet 50 is located on and bounded to a proper position of a receiver sheet with the binder 57, then the substrate 52 is separated; thus, a pattern and/or image is printed onto the receiver sheet. However, as per the conventional dye-sheet 50 being bounded to the receiver sheet, the thickness of the polyethylene terephthalate (PET) 56 plus the-polypropylene resin 59 will make the surface of receiver sheet irregular, and this may result in contamination which will affect the integrated appearance of the receiver sheet.